Plastic Lens Polymerization: Nonhalogenated Tin Catalyst and Diketone Control
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Solution Overview
Problem
Polythiourethane-based lenses prepared with amine-based catalysts exhibit color issues, leading to reduced total transmittance, and nonhalogenated tin-based catalysts face challenges in maintaining sufficient pot life and stability.
Innovation Solution
A polymerizable composition comprising a bi- or higher functional isocyanate compound, a bi- or higher functional thiol compound with sulfide or ester bonds, a nonhalogenated tin-based catalyst, and a diketone-based low-temperature reaction rate controlling agent, which controls reactivity and viscosity to enhance transparency and workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If amine-based catalysts are used for polymerization, then polymerization activity is improved, but the resulting lens exhibits color issues and reduced total transmittance
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by switching from amine-based catalysts to nonhalogenated tin-based catalysts (such as dibutyltin dilaurate, dimethyltin diacetate, or dioctyltin dibutoxide). This parameter change eliminates the coloration issue while maintaining polymerization activity through the use of a diketone-based reaction rate controlling agent.
Solution Approach 2:
The patent introduces a diketone-based reaction rate controlling agent (such as acetylacetone, benzoylacetone, or di(4-bromo)benzoylmethane) as an intermediary substance that mediates between the nonhalogenated tin-based catalyst and the polymerizable composition. This intermediary controls the reaction rate and enables the use of nonhalogenated catalysts without sacrificing polymerization efficiency.
2Object-affected harmful factors
If nonhalogenated tin-based catalysts are used to eliminate toxicity, then safety is improved, but pot life becomes insufficient and quality stability deteriorates
Solution Approach 1:
The patent changes the reaction kinetics parameters by introducing a diketone-based reaction rate controlling agent that slows down the polymerization reaction at low temperatures. This allows nonhalogenated tin-based catalysts to provide sufficient pot life (several hours to tens of hours) while maintaining quality stability throughout the polymerization process.
Solution Approach 2:
The patent implements a periodic temperature elevation strategy where the polymerization is carried out by gradually elevating temperature from low to high over several hours to tens of hours. The diketone-based reaction rate controlling agent enables this extended periodic process by maintaining stable reactivity throughout the temperature transition, ensuring sufficient pot life and quality stability.
3Stability of the object's composition
If halogenated tin-based catalysts are used to ensure sufficient pot life and stability, then process stability is improved, but human health safety deteriorates due to high toxicity
Solution Approach 1:
The patent changes the chemical composition parameters by replacing halogenated tin-based catalysts with nonhalogenated tin-based catalysts. The introduction of a diketone-based reaction rate controlling agent compensates for the lower inherent stability of nonhalogenated catalysts, maintaining sufficient pot life and quality stability without the toxic side effects of halogenated compounds.
Solution Approach 2:
The diketone-based reaction rate controlling agent serves as an intermediary that enables the use of nonhalogenated tin-based catalysts by modulating their reactivity. This intermediary substance allows the system to achieve the stability and pot life characteristics of halogenated catalysts while eliminating their toxicity, making the process both safe and stable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a stable pot life, improved reactivity, and transparency, preventing bubble generation and optical nonuniformities, while being harmless to humans, suitable for manufacturing various plastic lenses like eyeglass and camera lenses.
Implementation Method 1
a catalyst having a strong polymerization activity may be used, or an increased amount of a catalyst may be used
Implementation Method 2
the polymerization reaction is carried out over several hours to tens of hours while the temperature is gradually elevated from a low temperature to a high temperature
Data Source
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AI summary
An embodiment relates to a polymerizable composition for a plastic lens. The polymerizable composition for a plastic lens according to the embodiment comprises a nonhalogenated tin-based catalyst and a diketone compound as a low-temperature reaction rate controlling agent. Accordingly, the polymerizable composition has a more stable pot life so that the polymerization rate can be appropriately controlled, thereby improving the reactivity and the workability, and that the generation of bubbles are prevented, thereby improving the transparency of the resin.